1. Field of the Invention
This invention relates generally to the manufacturing of tape automatic bonded semi-conductor chips and more particularly to a structure and technique for improving the dynamic burn-in operation in the manufacturing process of mounting integrated circuit chips on electrical wires for further packaging.
2. Prior Art
One technique for mounting integrated circuit chips utilizes a process known as tape automated bonding (TAB). In this technique an elongated insulating tape is provided which has electrical circuit lines formed thereon by conventional plating and etching processes so as to form a series of locations along the tape with each location having the desired wire pattern on which each integrated circuit chip is to be bonded. Automated machinery passes the tape past a chip mounting station wherein the desired integrated circuit chips are attached serially along the tape to the wiring pattern formed at each location. As the chips are applied to the various locations individually, a testing function is performed along with the bonding operation to make an initial determination of chips which are clearly unacceptable. These chips may then be immediately removed and not further processed.
However, it is known practice in the art of tape automated bonding to perform an operation which is known as a "dynamic burn-in" of the chip. To perform this dynamic burn-in the chip is heated to about 120.degree. C. and a voltage in excess of normal operating voltage and signals are applied to various locations of the chip to exercise the chip. It has been found that this particular technique can be used to readily identify those chips that while apparently testing good in the initial testing phase nevertheless have a very early failure mode. The dynamic burn-in accelerates this early failure rate so that the chips may be identified as failed chips immediately following the dynamic burn-in operation and removed from further processing. It has also been suggested by some that the dynamic burn-in may in fact actually increase the life of an integrated circuit chip. In any event, the dynamic burn-in is conventionally performed as a part of the processing step in manufacturing TAB semi-conductor chips.
As indicated above, the dynamic burn-in requires power, and ground potential, as well as various signal levels to be applied to the chip. When the chip remains on the insulating tape, the geometry of the tape is such that only two different signal levels or power levels can be applied simultaneously to all of the chips; i.e. one level being applied by a line running down one margin of the chip and a second level applied by a line running down the other margin of the tape. Any additional signal or power levels would require crossing of wires which cannot be readily achieved in the process of forming wire patterns on the tape. Thus the dynamic burn-in of the chips has conventionally required the chips to be individually powered and signaled for this dynamic burn-in operation.